Any reasonable person must still have some doubt about this word, as all occurrences on the web of the "definition" given below seem to be traceable to the Grandiloquent Dictionary as the only source. It is a valid word in Scots Gaelic, where it can mean anything from a trip to a stroll to a scratch or scrape.
Wiktionary suggests that duais-scriob, meaning 'sweepstakes' comes from the word duais, a prize, and scriob meaning 'to sweep'.
Finally, someone called "muckefuck" over somewhere else on the web suggests, citing a reference called Dwelly:
There is a Scots-Gaelic word sgrìob which has the basic meaning of "scratch", but can also refer to "Itching of the lip, superstitiously supposed to portend a kiss (sgrìob-pòige), or sgrìob-dìghe (or sgrìob-drama), a dram." So the full expression should be sgrìob-dìghe ("drink-itch") or sgrìob-drama ("dram-itch").